Sorry, but this is going to be bad news.
The CGo3+ will not work on any Q500 series. Not even the Q500 4K. The camera gimbal is not coded to accept the pitch (tilt) signal from the Q500 series. And the video is not transmitted at a resolution the ST10 series controllers can use.
You can upgrade the Q500+ to provide power to the CGo3+, or you can do some soldering to add wires to the CGo3+ that can access the power plug on the Q500+, but you still will not have a workable camera. The camera will simply stabilize, point forward, and will not move in response to the controller. If you plan to fly with an ST10 series controller, the ST10 screen video will also be very broken up, pasted almost solid with artifacts, and all you will get is a broken glimpse of the view several seconds behind real time.
It would be best to find a CGo3. The CGo3 will work on your Q500+ without modification to the drone or the camera, as long as it comes with it's original "pigtail" adapter. The adapter was provided on the original kit to let the camera work on Q500 series drones that don't have the Q500-4K camera mount.